Synthesis of hierarchical porous carbon loaded with chlorine and its mercury removal performance
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摘要: 以纳米碳酸钙为模板，水稻秸秆为碳前驱体，采用共热解法制备了负载氯的分级多孔生物质炭。在模拟烟气条件下，利用固定床实验台架研究了生物质碳材料对烟气中的单质汞（Hg0）的脱除性能。采用扫描电镜（SEM）、透射电镜（TEM）、N2吸附-脱附（BET）、程序升温脱附（Hg-TPD）以及X射线光电子能谱（XPS）等方法对材料进行表征。结果表明，盐酸浸渍不仅可去除模板产物生成多孔结构，并且有效地将氯负载到材料表面。负载氯的分级多孔炭B1C1-Cl2的比表面积和总孔容分别达到398.1 m2/g和0.4923 cm3/g。在120℃，空速（GHSV）为225000 h-1时，脱汞效率可达95%。多孔结构有利于气体扩散，高比表面积为材料提供了更多的反应位点，微孔-介孔内表面上的C-Cl共价键为脱汞的主要化学吸附活性位点。Abstract: Chlorine-loaded hierarchical porous bio-char was prepared by co-pyrolysis using nano-CaCO3 as template and rice straw as carbon precursor. The removal of mercury (Hg0) from flue gas by porous materials was studied on a fixed bed test bench with simulated flue gas. The materials were characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM), N2 adsorption-desorption (BET), temperature programmed desorption (Hg-TPD) and X-ray photoelectron spectroscopy (XPS). The results show that HCl impregnation not only removes the products on the template to form porous structures but also effectively loads chlorine onto the surface of the material. The specific surface area and total pore volume of B1C1-Cl2 are 398.1 m2/g and 0.4923 cm3/g, respectively. When the GHSV is 225000 h-1 at 120 ℃, the removal efficiency of Hg0 by chemical adsorption is up to 95%. The porous structure is beneficial to gas diffusion and the high specific surface area can provide more active sites. The covalent groups (C-Cl) participating in the Hg0 removal process are the dominant chemical adsorption sites on the inner micro-mesopore surface.
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Key words:
- elemental mercury /
- porous bio-chars /
- chlorine /
- adsorption /
- flue gas
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图 2 B1C0和B1C1-Cl2的SEM和TEM照片
Figure 2 SEM images of B1C0(e) and B1C1-Cl2((a), (b)), and B1C1-Cl2((c), (d)), and TEM images of B1C0(f)
图 3 吸附剂的N2吸附-脱附曲线和孔径分布
Figure 3 N2 adsorption-desorption curves at 77 K (a), DFT pore size distributions by pore volume ((b), (c)) and DFT pore size distributions by surface area (d)
图 4 不同混合质量比的吸附剂对Hg0脱除效率的影响
Figure 4 Effect of sorbents with different mass ratios on removal efficiency of Hg0
图 5 HCl处理的吸附剂对Hg0脱除效率的影响
Figure 5 Effect of sorbents with HCl treatment on removal efficiency of Hg0
图 6 B1C1-Cl2和B1C2-Cl2的TPD实验数据及拟合分析图
Figure 6 TPD experimental data and fitting analysis of B1C1-Cl2 and B1C2-Cl2
表 1 吸附剂的孔结构参数
Table 1 Pore structural parameters of sorbents
Sorbent ABET/(m2·g-1) Pore volume v/(cm3·g-1) R/nm vT vmic vmes B1C0 88.29 0.1285 0.0000 0.0954 5.82 B3C1 329.5 0.3613 0.1003 0.1517 4.38 B2C1 560.2 0.6859 0.0315 0.4348 4.89 B1C1 591.3 0.5952 0.0683 0.4548 4.31 B1C2 742.5 0.6972 0.1020 0.4768 3.75 B1C3 428.7 0.4655 0.0387 0.3368 4.34 B1C1-Cl0.5 447.1 0.5107 0.0539 0.3598 4.32 B1C1-Cl2 398.1 0.4923 0.0548 0.3011 4.94 B1C1-Cl5 364.5 0.4188 0.0726 0.2175 4.59 
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表 2 XPS谱图中相关官能团含量
Table 2 Related functional groups obtained from XPS spectra
Sample Atom content/% >Relative intensity/% C Cl Ca Cl- C-Cl 2p3/2 C-Cl 2p1/2 B1C0 90.5 0.40 0.07 23.08 19.20 57.71 B1C1-Cl2 88.5 1.50 0.10 2.36 63.68 33.95 B1C2-Cl2 68.93 1.25 0.17 6.13 59.68 34.18
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